Drill bit and method for producing a drill bit

ABSTRACT

A drill bit including a shaft which has a pyramidal shaped end defining a drill tip with a plurality of edges defining the pyramidal shape. 
     One or more recesses are provided for directing away debris produced while drilling, the at least one recess having a first portion extending along the shaft and a second portion having a first portion extending along the shaft and a second portion which extends along the drill tip; wherein the. The second portion which extends along the drill tip. The second portion of the at least one recess extends along an edge of the drill tip.

RELATED APPLICATIONS

This is a continuation of U.S. patent application Ser. No. 13/862,122,filed Apr. 12, 2013, which is a continuation of U.S. patent applicationSer. No. 13/325,483, filed Dec. 14, 2011, which is a continuation ofU.S. patent application Ser. No. 12/243,802, filed Oct. 1, 2008, whichis a continuation of U.S. patent application Ser. No. 10/513,259 filedMay 11, 2005, which is the national stage, filed on May 11, 2005, ofInternational Application Serial No. PCT/AU2003/001003, having aninternational filing date of Aug. 7, 2003, which claims priority toAustralian Patent Application Serial No. 2002950673, filed Aug. 8, 2002and Australian Patent Application Serial No. 2002953610, filed Nov. 8,2002, all of which applications are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a drill bit and method for producing adrill bit, and is of particular but by no means exclusive application todrilling bones, cartilage and similar structures during orthopaedicsurgery.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention, there is provideda drill bit comprising:

a shaft which has a pyramidal shaped end defining a drill tip with aplurality of edges defining the pyramidal shape; and

one or more recesses for directing away debris produced whilst drilling,the or each recess having a first portion extending along the shaft anda second portion which extends along the drill tip, wherein the secondportion of the or each recess extends along an edge of the drill tip.

Preferably, each edge defines a cutting edge and preferably the or eachrecess. is located to further define the cutting edge.

Preferably each edge extends from the shaft to a remote point of thedrill tip.

By employing a cutting edge the drill tip can quickly create a securinghole which secures the drill bit in position so as to prevent the drillbit from moving over the surface of the material when starting to drill.

Preferably, the depth of the second portion of each of the recessesvaries along a length thereof relative to a surface of the drill tip sothat the cutting ability of the edge adjacent to the point of the drillbit is less than the cutting ability of the edge adjacent to the shaft.

By reducing the cutting ability of the cutting edge adjacent to thepoint, the drill bit is less likely to break when drilling is commenced.This is because the edge adjacent to the point is less likely to lockwith the material into which the drill is entering.

Preferably, the first portion of the or each recess is substantiallyhelical in shape, whilst the second portion of the or each recess issubstantially straight.

Preferably, the drill tip includes at least three edges which define thepyramidal shape of the drill tip.

Preferably, at least three corresponding surfaces extend between thethree edges. Prior to forming the or each recess the surfaces may beflat (planar) or concave with respect to the drill bit.

Preferably, the second portion of the or each recess extends along arespective one of the surfaces.

Preferably, the edge of the drill tip is bevelled so as to enhance thecutting ability of the cutting edge.

According to a second aspect of the present invention, there is provideda method for producing a drill bit, including the steps of:

forming a shaft which has a pyramidal shaped end defining a drill tipwith a plurality of edges defining the pyramidal shape; and

forming one or more recesses for directing away debris produced whilstdrilling, the or each recess having a first portion extending along theshaft and a second portion which extends into the drill tip, wherein thesecond portion of the or each recess extends along an edge of the drilltip.

Preferably, the step of forming the one or more recesses includes movinga grinding element outwardly from the drill tip as it moves therealongsuch that the depth of the second portion of each of the recesses variesalong a length thereof relative to a surface of the drill tip.

Preferably, the or each recess is formed adjacent to a respective edgesuch that the cutting ability of the edge adjacent to a point of thedrill tip is less than the cutting ability of the edge adjacent to theshaft.

According to a third aspect of the present invention, there is provideda drill bit comprising:

a shaft having a drilling end defining a drill point;

at least one face that extends to and helps define the drill point, theor each face generally subtending an acute angle with a longitudinalaxis of the shaft; and

at least one flute defined in the shaft for directing away debrisproduced during drilling, with the at least one flute intersecting withthe at least one face, such that, in end view, the flute is offset froma central part of the face.

By offsetting the flute in this manner, the present inventor hasdiscovered that eg. bone debris can be rapidly released and directedaway from the drill end, and yet a strong drill point can be formedwhich can be securely located at the bone. The inventor has observedthat a strong point can be forced through the periosteum to provide ameans against slippage and to then enable rapid drilling of the bone.Such a drill point may also preliminarily puncture the bone and then,when driven, cut away the bone, the flute location then rapidlydirecting away debris produced during such cutting.

Preferably, the flute intersects the face in a manner that defines acontinuous curve at the flute-face intersection.

This curving further enhances and smooths the directing away of debrisproduced during bone drilling.

Preferably the or each face:

-   (a) is flat, being defined as a bevel;-   (b) is curved or v-shaped concavely into the shaft;-   (c) has a chamfer or a v-shaped groove along one edge thereof.

Thus, in the third aspect when it is stated that the face generallysubtends an acute angle with a longitudinal axis of the shaft, forcurved faces this acute angle is represented by an imaginary line drawnfrom the drill point to where the face meets the shaft exterior surface.

In (a) the provision of one or more flat bevelled faces at the drillingend enables a rapid and precise formation of the drill point, and alsoprovides a definite and strong point structure to maximise the life ofthe drill point. In (b) and (c) the concave shaping of the face canenhance its capacity to cut and may even further strengthen the drillpoint.

Preferably, in (c) the flute extends into the face adjacent to said oneedge.

Optionally in (c) the flute can intersect with the v-shaped groove.

This further enhances the directing away of debris produced during drillcutting.

In one preferred form three faces are provided at the drilling end, eachevenly offset with respect to the other two and each tapering down tothe drill point to provide the drill end with the appearance of atriangular pyramid. Preferably in this regard a respective flute isprovided to intersect with each face.

In an alternative form four faces can be provided at the drilling and,each evenly offset with respect to adjacent faces on either side thereofand each tapering down to the drill point to provide the drill end withthe appearance of a square pyramid. In this regard a respective flutecan be provided just to intersect with each of only two of the faces,being opposing faces at the drill end (or a flute for each face may alsobe provided).

Whilst three or four faces have been found to be optimum, any number offaces at the drilling end may be employed as appropriate.

Preferably, the or each flute extends generally spirally away from itsrespective face and at least part way along the shaft.

Typically the fluting does not extend for the full length of the shaftto provide, for example, an unfluted part of the shaft which can beinserted into the drive of a drill.

According to a fourth aspect of the present invention, there is provideda drill bit comprising:

shaft having a drilling end defining a drill point;

at least one face that extends to and helps define the drill point, theor each face generally subtending an acute angle with a longitudinalaxis of the shaft; and

at least one flute defined in the shaft for directing away debrisproduced during drilling, with the at least one flute intersecting withthe at least one face such that a continuous curve is defined at theflute-face intersection.

According to a fifth aspect of the present invention, there is provideda drill bit comprising:

a shaft having a drilling end defining a drill point;

at least one face that extends to and helps define the drill point, theor each face generally subtending an acute angle with a longitudinalaxis of the shaft; and

at least one flute defined in the shaft for directing away debrisproduced during drilling, with the at least one flute intersecting withthe at least one face, wherein the or each face:

(a) is curved or v-shaped concavely into the shaft;

(b) has a chamfer or a v-shaped groove along one edge thereof.

Preferably, the surgical drill bit of the second and third aspects isotherwise as defined in the third aspect.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

Notwithstanding any other embodiments which may fall within the scope ofthe present invention, a preferred embodiment of the present inventionwill now be described, by way of example only, with reference to theaccompanying drawings, in which:

FIG. 1 illustrates a perspective view of a first drill bit according toa preferred embodiment of the present invention; and

FIG. 2 illustrates an end view of the first drill bit shown in FIG. 1.

FIGS. 3A to 3C respectively show an enlarged end, and side andperspective views of a second drill bit in accordance with the preferredembodiment of the present invention;

FIGS. 4A to 4D respectively show front, end, side and perspective viewsof the second drill bit of FIG. 3, but in outline;

FIGS. 5A to 5C respectively show an enlarged end, and side andperspective views of a third drill bit in accordance with the preferredembodiment of the present invention;

FIGS. 6A to 6C respectively show an enlarged end, and side andperspective views of a fourth drill bit in accordance with the preferredembodiment of the present invention;

FIGS. 7A to 7D respectively show an enlarged end, and side, perspectiveand reverse perspective views of a fifth drill bit in accordance withthe preferred embodiment of the present invention;

FIGS. 8A to 8C respectively show an enlarged end, and side andperspective views of a sixth drill bit in accordance with the preferredembodiment of the present invention;

FIGS. 9A to 9C respectively show an enlarged end, and side andperspective views of a seventh drill bit in accordance with thepreferred embodiment of the present invention; and

FIGS. 10A to 10C respectively show an enlarged end, and side andperspective views of a eighth drill bit in accordance with the preferredembodiment of the present invention.

PREFERRED EMBODIMENT OF THE PRESENT INVENTION

FIGS. 1 and 2 show a first drill bit 101 according to the preferredembodiment of the present invention. The drill bit 101 includes a shaft112 which has a pyramidal shaped end 118 defining a drill tip. Thematerial from which the drill bit 101 is made depends on the intendedapplication of the drill bit 101. However, for orthopaedic surgery, thedrill bit 101 is made from surgical quality stainless steel. Whilst notillustrated in FIG. 1, the other end of the drill bit 101 is adapted formounting in a motorized drill chuck. For example, the other end of thedrill bit 101 can be provided with a series of graduations, a cut-awayand a circumferential groove in the shaft 112 adjacent the other end soas to facilitate its coupling in the chuck of a drive of a motorisedsurgical drill. The graduations can be used to indicate depth ofinsertion of the drill bit into the drive chuck and into the patient.

The drill bit 101 also includes three recesses in the form of grooves117 a, 117 b and 117 c (collectively referred to as reference numeral117), each of which includes a first portion 125 a, 125 b and 125 c(collectively referred to as reference numeral 125) extending at leastpartway along the shaft 112 and a second portion 111 a, 111 b and 111 c(collectively referred to as reference numeral 111) which extends edges113 a, 113 b and 113 c (collectively referred to as reference numeral113) of the drill tip. Typically edges 113 define a cutting edge. Theedges 113 also include bevelling so as to enhance the cutting ability ofthe cutting edge. The grooves 117 allow debris which is produced whilstdrilling to be channeled away from the hole while being drilled. Thefirst portion 125 of each of the grooves 117 spirals along the shaft 112so as to form of a helix, whilst the second portion 111 is substantiallystraight (that is, tending to align with a longitudinal axis of theshaft). Each of the grooves 117 typically has an arcuatesemi-cylindrical shape in cross-section and along its length. However,other suitable profiles such a V-shape or square shape may be employed.

The depth of the second portion 111 of each of the grooves 117 variesalong the length of the second portion 111 relative to the surface ofthe drill tip in which the second portion 111 is located. Morespecifically, the depth of the second portion 111 of each of the grooves117 becomes shallower towards the point 119 of the drill bit 101. Thisprovides the portion of the cutting edge 113 located nearer the point119 with a lesser cutting ability than the portion of the cutting edge113 located nearer the shaft 112. The advantage of this is that thedrill tip is less likely to break as a result of locking with thematerial into which the drill bit 101 is entering.

The pyramidal shaped end 118 is formed from three elongate surfaces 120a, 120 b and 120 c (collectively referred to as reference numeral 120),but more surfaces can be employed if desired. Increasing the number ofsurfaces to define the pyramidal shaped end 118 results in more edges113 which can define more cutting edges.

Also, the pyramidal shaped end 118 is relatively longer than the drilltip of existing drills. This provides an extreme point 119 which assistsin securely locating the drill bit 101 so as to prevent movement thereofwhen drilling is started. The assistance is provided as a result of theextreme point 119 piercing the periosteum and puncturing the outersurface of the bone, thereby locating the drill bit 101 in place priorto drilling. Each of the surfaces forming the pyramidal shaped end 118subtends an angle with the longitudinal axis of the drill bit 101. Theangle is typically around 30°, but may be varied depending on theapplication (for example, hardness of the material to be drilled).

As mentioned previously, the drill bit 101 is made from a material thatis suitable for the intended application. For example, where the drillbit 101 is intended to be used in orthopaedic surgery the drill bit 101is made from surgical quality stainless steel. The drill bit 101 is madefrom a blank rod of the appropriate material. Using a suitable grinder,one of the ends of the blank rod can be ground down so as to form thepyramidal shaped end 118 and adapt the other end of the drill bit 101 sothat the drill bit 101 can be retained by a chuck of a drill.

The grinding machine can also be used to form the grooves 117. Whenforming the first portion 125 of each of the grooves 117, the grindingwheel of the machine remains fixed so that the first portion 125 has aconstant depth. However, when forming the second portion 111 of thegrooves 117, the grinding wheel is gradually moved outwardly from thedrill tip as it moves towards the point 119. Moving the grinding wheeloutwardly results in the second portion 111 having a depth that variesalong the length of the drill tip. This characteristic produces acutting edge which has a lesser cutting ability about the point 119 andwhich increases in cutting ability towards the shaft 112. Having alesser cutting ability at the point 119 reduces the likelihood of thepoint 119 breaking off when drilling is commenced due to the cuttingedge locking with the material into which the hole is being drilled.

Referring to FIG. 3, which shows a second drill bit 310, the drill bit310 includes a drill shaft 312, the opposite end 313 of which is adaptedfor mounting in a motorised drill chuck. For example, for orthopaedicprocedures, the opposite end of the shaft can be provided with a seriesof gradations 314, a cut-away 315 and a circumferential groove 316adjacent to end 313 to facilitate its coupling in the chuck of a driveof a motorised surgical drill. The gradations can be used to indicatedepth of insertion of the drill bit in both the drive chuck and into apatient.

Three spiral flutes 317 extend from near the drilling end 318 and partway along the shaft 312. Each flute is typically an arcuatesemi-cylindrical groove extending in the shaft, but may be V-shaped,square shaped etc. in cross-section. Each flute provides a passagewayfor the release of debris cut by the drill bit as it is inserted througha substrate (typically a bone). Usually two or three such spiral flutesare provided in the drill bit to maximise debris release.

A drill point 319 is provided at drilling end 318, the drill point beingsubstantially elongated, tapered and pointed when compared with aconventional drill bit. In effect, the drill point is provided as atrocar-type formation.

Further, one or more, and typically three, beveled faces 320 areprovided and combine to define the drill point 319 at drilling end 318,each face subtending an angle α with a longitudinal axis AX through theshaft 312. Typically, the subtended angle α is around 30°, although itmay be varied depending on the application (eg. hardness of material tobe drilled). The three faces generally provide end 318 with a triangularpyramidal appearance.

Advantageously, the formation of bevelled faces 320 define cutting edges322 along the side of each bevelled face which facilitate cutting andthus drilling into a bone or similar when the drill bit is rotated.

The formation of an extreme drill point 319 at drilling end 318 alsoenables the drill to be securingly located at a bone, piercing theperiosteum and puncturing the outer surface of the bone to locate thedrill bit in place prior to drilling.

In accordance with the present invention, and as best shown in FIG. 3A,each flute 317 intersects with a respective face 320 at a location thatis offset from a centre line CL through the face 320. The advantage ofthis offsetting is that it facilitates maximum debris removal duringcutting of bone, cartilage and other bodily material.

For example, referring to FIG. 3A, and assuming a counter clock-wiserotation of the drill, uppermost face 320′ defines a leading edge 322′and a trailing edge 322″. It will be see that flute 317′ is locatedadjacent to the trailing edge. Thus, as the drill rotates and leadingedge 322′ cuts through a material, debris passes across and isaccommodated by a maximal face area 320′, prior to passing into flute317′. This maximal face area prevents bunching or blocking of debris atthe face and enhances debris release away from the drill point.Therefore, an optimal location for the intersection of each flute withits respective face is adjacent to the trailing edge for that face, asshown in FIG. 3A. Advantageously, rapid debris removal also facilitatesmore rapid drilling.

Referring now to FIGS. 5A to 5C, where like reference numerals are usedto denote similar or like parts, drilling end 518 is now provided withfour bevelled faces 520 (which in this embodiment are typically flatfaces). The four faces generally provide end 518 with a square pyramidalappearance.

As can be clearly seen from FIG. 5A, only two of the faces (in this casetwo opposing faces) are provided with a flute 517 intersectingtherewith. Again, these flutes are offset from a central part of theirrespective face to enhance debris removal as described above. Theunfluted faces also provide an enhanced trocar-like affect to thedrilling end 518.

It will also be seen in FIG. 5 that the flutes 517 are enlarged comparedwith the flutes of the drill bit of FIGS. 3 and 4. This is to ensurethat the rate of debris release is maintained with the lesser flutenumber, and this also enables the flutes to pick up debris that passesacross the unfluted faces (ie. as the drill rotates at rapid speeds).Otherwise, the operation of the drill bit is the same as the drill bitof FIGS. 3 and 4.

Referring now to FIG. 6, where like reference numerals are used todenote similar or like parts, a surgical drill bit having three faces atdrilling end 618, similar to the drill bit of FIGS. 3 and 4, is shown.Each face also has a respective flute intersecting therewith, however,in this embodiment the intersection between the flute and its respectiveface is not abrupt but is gradual as facilitated by a continuous curvedregion 626. This region provides a kind of scalloping or concavity ineach face 620, thus enhancing the definition of the drill point 619, butalso providing a more pronounced channelling affect into each flute toguide and enhance the removal of debris cut by the rotating drill bit.

The more pronounced drill point facilitates easier drill bit location atslippery cutting surfaces and easier penetration. The region 626facilitates more rapid removal of debris and thus even faster drillcutting.

Referring now to FIGS. 7A to 7D, the drill bit of FIG. 6 is furthermodified in that each face 720 is concaved inwardly with respect to thedrill bit, defining an arcuate 3D scalloped surface. This is best seenwith reference to FIG. 7D.

The effect of this scalloping is that the drill point 719 is evenfurther pointed or sharpened, and the cutting edges become curved alongtheir length and again are further sharpened (ie. because of the morerapid dropping away of each face 720 on either side of the cuttingedge).

The drill bit of FIG. 7 also employs the continuous curved region 726 atthe intersection of flute 717 and face 720 so that debris cut by thedrilling end is rapidly conveyed away therefrom in use.

In FIG. 7, in end view (ie. FIG. 7A) the concave face is typicallysymmetrical about face centre line CL. However, the concave face can bedefined asymmetrically about the centre line, for example, so thatadjacent to the leading edge 722′, the face slopes more steeply away,and slopes more gradually up towards the trailing edge 722″. Thisasymmetric offset of the concavity at each face can sharpen the leadingedge relative to the trailing edge and can enhance debris being directedtowards flute 717 (ie. by pressure differentials etc.). The operation ofthe drill bit of FIG. 7 is in other respects similar to that previouslydescribed.

Referring now to FIG. 8, the inwardly concave curved face of FIG. 7 isreplaced by two flat sub-faces 827 and 828. The sub-faces 827 and 828 inend view (ie. FIG. 8A) define face 820 as a type of tapering V-shapedgroove (ie. tapering down to drill point 819). Again, the employment ofa concave V-shaped face 820 sharpens or pronounces the edges 822, andalso assists in directing debris towards flute 817 via curved region826.

Again, typically the sub-faces 827 and 828 are arranged symmetricallyabout face centre line CL, but may be asymmetrically offset to eg. moresteeply slope away from the leading edge 822′ as opposed to the trailingedge 822″. Again, this can define a sharper cutting edge and assist withthe distribution of debris away from the drilling end•818.

Referring now to FIGS. 9A to 9C, where like reference numerals are usedto denote similar or like parts, a drill bit having either flat faces920 as shown in FIG. 6, or curved faces as shown in FIG. 7 is depicted.In any case, in this embodiment a chamfer 930 is provided that slopesaway from the leading edge 922 and into its respective face as bestshown in FIG. 9A. As also best shown in FIG. 9A, a small section 931 ofchamfer 930 continues on and extends partway up trailing edge 922″, sothat drill point 919 is defined by the merging of three chamfered facesand thus is unitary and pyramidal in shape (ie. trocar-like).

This chamfering arrangement increases the strength of the drill pointand prevents it from breaking away where other point configurationsmight otherwise fail in extreme situations. Otherwise, the drill bit ofFIG. 9 is similar in construction to the drill bit of FIGS. 6 and 7 andoperates in a similar manner to the drill bits previously described.

Referring now to FIGS. 10A to 10C, where like reference numerals areused to denote similar or like parts, a further modified drill bit isshown. In this embodiment, the faces 1020 are typically flat (althoughmay be slightly concave) in a similar manner to FIG. 3. Also, in thisembodiment no continuous curve region at the intersection of flute 1017and face 1020 is depicted, although such a region may be provided asappropriate.

Unique to this embodiment is the provision of a V-shaped groove 1032running along the trailing edge 1022″, from the drill point 1019 to theflute 1017. The V-shaped groove 1032 terminates in the flute 1017 andprovides a further means for the channelling and directing of debrisinto the flute. In addition, it sharpens the leading edge 1022′ of eachface 1020, thus enhancing cutting. It also provides for the release ofdebris entrained in front of the leading edge as the drill bit rotates.The V-shaped groove 1032 can be symmetric or asymmetric as describedabove, with the advantages as described above.

Furthermore, in this embodiment at drill point 1019, in effect sixcutting edges are provided to further enhance insertion of the drill bitthrough the periosteum and to promulgate rapid cutting of the drill bitinto bone etc.

The operation of the drill bit of FIG. 10 is otherwise as described forthe previous drill bits.

Typically the flutes, faces and grooves are machined onto the shaft1012, and typically the shaft 1012 is formed from surgical stainlesssteel.

The shaft is typically cylindrical and circular in cross-section,although other cross-sectional shapes (eg. hexagonal or octagonal) maybe employed.

Those skilled in the art will appreciate that the invention describedherein is susceptible to variations and modifications other than thosespecifically described. It should be understood that the inventionincludes all such variations and modifications which fall within thespirit and scope of the invention.

The invention claimed is:
 1. A medical device for use during surgery,said device comprising a shaft and a tapered tip for drilling into asurface of body material; the tip including a plurality of faces, eachface having at least two sub-faces formed and arranged to define agenerally pyramidal shaped remote end terminating in an extreme drillpoint whereby the remote end is adapted to pierce the surface andthereby locate the tip prior to drilling; and wherein the shaft and tipincludes at least one flute having a first portion and a second portion;wherein the first portion is generally helical and extends at leastpartially along the shaft; wherein the second portion is formed in thetip and associated with a respective sub-face and extends partway alongthe tip behind the drill point; wherein the second portion includes agroove formed in the tip and adjacent at least one edge of therespective sub-face, thereby to enhance the cutting ability of the tip;wherein the first portion intersects with the second portion to directdebris away from the tip during drilling; and wherein the sub-faces areasymmetrically offset about a center line of the respective face.
 2. Themedical device according to claim 1, wherein the groove is a generallyconcave recess.
 3. The medical device according to claim 1, wherein thegroove is generally V-shaped.
 4. The medical device according to claim1, wherein the groove terminates in the shaft.
 5. The medical deviceaccording to claim 1, wherein the associated edge along which the grooveextends is a trailing edge of one face of said plurality of faces. 6.The medical device according to claim 1, wherein the tip includes twofaces and each face includes two sub-faces.
 7. The medical deviceaccording to claim 1, wherein said at least one flute includes twoflutes, said two flutes arranged such that the respective secondportions of each flute are associated with opposing sub-faces of thetip.
 8. The medical device according to claim 1, wherein a sub-face ofat least one face is defined by a chamfer.
 9. The medical deviceaccording to claim 1, wherein each sub-face is substantially flat. 10.The medical device according to claim 1, wherein at least one sub-faceof a face includes a curved portion.
 11. The medical device according toclaim 1, wherein the cutting ability of the edges adjacent to the remoteend of the tip is less than the cutting ability of the edges adjacent tothe shaft.
 12. The medical device according to claim 1, wherein saidshaft includes a longitudinal axis, and each of the faces generallysubtends at an angle of less than 30 degrees with respect to thelongitudinal axis of the shaft.
 13. The medical device according toclaim 1, wherein the at least one flute is arranged, such that, in endview, the flute is offset from a central part of the face.
 14. Themedical device according to claim 1, wherein the shaft is cylindrical.15. The medical device according to claim 1, wherein the shaft and tipare formed from stainless steel.